Voltage jump

For intermediate time resolutions (of the order of r ) the bulk capacitor has become impermeable, and the boundary circuit is relevant for the time dependence (second term in Eq. (64)) term 1 is constant, while term 3 is still zero. Finally in the long-time regime, at t rs, the stoichiometric polarization occurs while both bulk and boundary responses constitute the initial voltage jump from U= 0 to 11 = If (/ , + R ) note that both corresponding capacitors are completely impermeable, i.e., terms 1 and 2 are constant. In the steady state (f rs) all the capacitors block, and R + Kon 316 obtained as the stationary resistance value. Obviously time-resolved dc experiments allow the partial conductivities and the capacitances to be measured together with the chemical diffusion coefficient (ts ccl/Cf). The switching-off behavior is analogous. 

There is a lot of information available about the rate of action of channel blocking antagonist because this is relatively easy to determine by single-channel methods and also can often be obtained by macroscopic methods like voltage jump relaxations [e.g., Colquhoun et al. (55)] or noise analysis (107). 

A better understanding of the activator-veratridine interaction would require single-channel experiments which, however, are scarce. In cultured cardiomyocytes a mixture of veratridine and ATX II induces, on steady depolarization, frequent openings to a low conductance substate (y=4.6 pS). This can be seen in veratridine alone only after voltage jumps and for a short time whereas in ATX II alone a different substate (7 11.5 pS) is observed. In the mixture the state of low conductance is often preceded by openings of the largest conductance pS all... 

The initial voltage jump and the presence of resistance as discussed above can most reasonably be accounted for by means of a flux jump. A flux jump is defined as the sudden change in flux density over a finite volume. That a finite volume must be involved follows from Maxwell s equations, which prohibit spatial field discontinuities, as this would require infinite current densities at the location of the discontinuity. 

Question by H. R. Whittle, UKAEA Culham Laboratory How did you detect voltage jumps at the instant of coil transition to normal Was your oscilloscope connected to a search coil or to the terminals of the solenoid ... 

Answer by Author Voltage jumps associated with a flux jump, can be observed on the oscilloscope connected either to the solenoid terminals (see Fig. 6) or to a search coil (see Fig. 7). The solenoid itself initially behaves much like a search coil. 

G. Boheim, H.A. Kolb, Analysis of the multi-pore system of alamethicin in a lipid membrane. I. Voltage-jump current-relaxation measurements, J. Membrane Biol. 38 99-150 (1978)... 

To understand the role of pluronics as membrane permea-bilizers, the transport of various small molecules across PC lipid bilayers in the presence of pluronics was examined. To measure the transport of weak acids across planar bilayer membranes (spread over a perforated polytetrafluoroethylene (PTFE) sheet), the corresponding shifts in pH were observed. The addition of pluronic was shown to drastically increase the rate of the weak acid 2-n-undecyl malonic acid transport across the bilayer (Figure 3). This effect increased with increasing concentration of pluronic. This effect was present, though slower, when the pluronic was added to the opposite side of the bilayer from the acid. There were also similar, but far less pronounced, effects on the transport of acetic acid and ammonium. The authors observed that a voltage jump aaoss the membrane in the presence of tetraphenyl borate (TPB ) ion introduced an exponentially decaying current as the ions moved aaoss the membrane. Similar to the pH measurements, the current decay curve in the presence of pluronics showed that TPB" transport occurs much faster in the presence of... 

As shown in fig. 1, for a small bias current just above the critical current /c, the junction exhibits a periodic voltage jump. For a laige bias current, larger hysteresis and negative resistance were observed. 

The peaks on the oscillogram correspond to the arrival of the detonation wave at the probes. The time interval needed for the detonation wave to travel the distance between the two probes is calculated knowing the time scale (b) and the distance between two voltage jumps—assigned as Iq in the oscillogram. The time scale, which is expressed in pm/cm, is calculated according to the equation... 

In nearly in all the experiments a film formed on the anode after a rather long electrolysis. In the course of the time it cracked and separated from the base and was perhaps the cause of voltage jumps in the bath which were observed from time to time. The composition of the film could not be determined with x-ray phase analysis, but probably consisted of tantalum and calcium oxides. 

Compared to other methods, the current interrupt method has the advantage of relatively straightforward data analysis. However, one of the weaknesses of this method is that the information obtained for a single cell or stack is limited. Another issue with this method is the difficulty in determining the exact point at which the voltage jumps instantaneously thus, a fast oscilloscope should be used to record the voltage changes. 

Sargent DF (1975) Voltage jump/capacitance relaxation studies of bilayer structure and dynamics studies on oxidized cholesterol membranes. J Membr Biol 23(1) 227 247 Hianik T, Krivanek R, Sargent DF, Sokolikova L, Vinceova K (1996) A study of the interaction of adrenocorticotropin-(l-24)-tetracosapeptide with BLM and Uposomes. Progr Coll Polym Sci Trends Colloid Interface Sci X 100 301-305... 

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